CAT continues to plague commercial and military aircraft. CAT represents more than just an annoyance to passengers; it is a distraction to the flight crew, it consumes extra fuel (by reducing fuel efficiency and by requiring horizontal diversions around regions of suspected CAT), and it contributes to airframe metal fatigue leading to structural failure during flight and landings.
A new type of unmanned vehicle is being designed for military reconnaissance. Some of these vehicles have large wingspans, fly slowly, and cannot tolerate moderate turbulence because of their vulnerability to unrecoverable aerodynamic upset. These reconnaissance aircraft also need a CAT prediction capability in order to avoid such turbulence.
In the field of CAT prediction, key factors that determine Richardson Number (Ri) are vertical air temperature gradient and vertical wind shear. Since low values of the Richardson Number are known to be necessary for production of CAT, it is important to have on board an aircraft the facilities for monitoring Ri, or its reciprocal RRi, for predicting in real time when and where CAT will occur and how severe it will be.